The present invention relates to plastic containers, preferably for non-carbonated food products. More particularly, the present invention relates to molded plastic containers, such as injection molded and/or blow molded plastic containers, having a layered or coated structure, especially having a coating on the internal surface thereof, as a carbon coating.
It is highly desirable to provide an effective and low cost way of overcoming the porosity of plastic containers and the problems attendant thereon.
Plastic containers and multi-layered plastic containers are commonly used for packaging items in a wide range of fields, including food and beverage, medicine, health and beauty, and home products. Plastic containers are known for being easily molded, cost competitive, lightweight, and are generally suitable for many applications. Multi-layered plastic containers provide the benefit of being able to use different materials in each of the layers, wherein each material has a specific property adapted to perform a desired function.
Because plastic containers may permit low molecular gases, such as oxygen and carbon dioxide, to slowly permeate through their physical configurations, the use of plastic containers sometimes proves to be less desirable when compared to containers formed from other less permeable materials, such as metal or glass. In most applications, the shelf life of the product contents is directly related to the package's ability to effectively address such molecular permeation. In the case of non-carbonated beverages, such as juices, oxygen in the atmosphere surrounding the container can gradually permeate inwardly through the plastic walls of the container to reach the inside of the container and deteriorate the contents. A highly porous container can permit rapid deterioration of the flavor of the container contents.
To address some to the foregoing concerns, plastic container manufacturers have utilized various techniques to reduce or eliminate the absorption and/or permeability of gases in plastic containers. Some of the more common techniques include: increasing the thickness of all or portions of the walls of the container; incorporating one or more barrier layers into the wall structure; including oxygen-scavenging or reacting materials within the walls of the container; and applying various coatings to the internal and/or external surface of the container. However, a number of conventional barrier and/or scavenger materials will not effectively curtail permeation through a highly porous container wall, especially over extended periods of time. Moreover, there are usually other practical concerns associated with most conventional techniques, most commonly, increased material costs and/or production inefficiencies.
In recent times, the use of plastics has become a significant social issue. Recycling has become an increasingly important environmental concern and a number of governments and regulatory authorities continue to address the matter. In a number of jurisdictions, legislation pertaining to the collection, return, and reuse of plastic containers has either been considered or has already been enacted. However, recycled material generally cannot be used in contact with the contents of most containers.
It is highly desirable to provide an effective, efficient and low cost process for coating the internal surface of a plastic container to address the foregoing problems and if desired permit the use of recycled content in the outer layer or layers of the container.
Processes have been developed for coating the internal surface of a container, as with a thin carbon coating, in order to address these problems. However, it is desirable to carefully control the thickness parameters of the coating.
Therefore, a need exists in the industry and it is an object of the present invention to provide a process and apparatus for use in the coating process of a plastic container in the testing of the coating parameters, especially the internal surface thereof, as for example, with a carbon coating.
It is a further object of the present invention to provide a process and apparatus as aforesaid which is effective, efficient and low cost.
Further objects and advantages of the present invention will appear hereinbelow.